2. Why is the Koch brothers-backed Americans for Prosperity getting involved in a small Wisconsin county race? Chris Hayes has the whole story. Joining him to discuss is Editor at Progressive Magazine, Ruth Coniff.

4. FiveThirtyEight’s Nate Silver has spoken: There’s a slight chance Democrats will lose the Senate majority. Generally, Silver’s forecasts are looked upon favorably by liberals. Not this time. Joining All In are Host of Majority Report, Sam Seder, Communications Director of Emily’s List, Jess McIntosh, and Senior Fellow at the Center for American Progress Action Fund, Aisha Moodie-Mills.